Self-aligning roller bearings are widely used as roll neck bearings of various types, bearings for vehicles, and bearings for various industrial applications.
It is known that the life of such a self-aligning roller bearing is shortened by troubles such as an increase in friction and heat generated inside the bearing which results in rolling contact fatigue when certain rollers do not rotate in a normal condition during the operation of the same, for example, in case that the roller rotates at a great negative skew angle.
Under the circumstance, various techniques have been developed to control the skew angle of a roller in operation. For example, method of processing have been proposed (see JP-B-57-61933), in which raceway surfaces of an inner ring and an outer ring are made different from each other in surface roughness (the surface roughness of the raceway surface of the outer ring is made higher than the surface roughness of the raceway surface of the inner ring).
As measures to avoid a great negative skew angle, methods have been proposed, in which at least either raceway surfaces or roller contact surfaces of inner and outer rings are provided with surface roughness which is different between parts of the surfaces in the neighborhood of the center of the bearing and parts of the surfaces in the neighborhood of sides of the bearing (see Japanese Patent No. 2900527).
One means for solving the problem included in the proposals is a configuration in which “the surface roughness of an outer ring raceway surface in parts thereof in contact with the roller located in the neighborhood of sides of the bearing is lower than the surface roughness of a part in contact with the roller located at least in the neighborhood of the center of the bearing other than the parts in contact with the roller” (see JP-A-11-226855).